Method of and apparatus for nonarcing circuit interruption



G. E. DOAN May 2, 1939.

METHOD OF AND APPARATUS FOR NONARCI NG CIRCUIT INTERBUPTION Filed June12, 1955 gNVaTOR 79M? Zia w ATTORN EYS Patented May 2, 1939 UNlTEDSTATES PATENT OFFICE METHOD OF AND APPARATUS FOR NON- ARCING CIRCUITINTERRUPTION 8 Claims.

The object of my invention has been to provide for the prevention of theformation of arcs during the interruption of electric circuits, and tosuch ends, my invention consists in the method of, and apparatus for,substantially non-arcing circuit interruption hereinafter specified.

In the accompanying drawing:

Fig. 1 is a diagrammatic representation of a form of apparatus,embodying my invention, and

19 Fig. 2 is a diagrammatic representation of another form of apparatus,embodying my inventicn.

While I shall illustrate my invention by the best embodiments thereofknown to me, it is to be understood that my invention is capable ofembodiment in many different forms, and for many different uses, andthat it is not to be confined, either as to the method or apparatusaspects thereof, to the examples herein chosen for go illustration. Myinvention is based upon the following research:

Whereas, a stable are forms at the opening of an electrical circuitunder ordinary conditions; that is, an arc which for a given potentialdifferg5 ence between the electrodes, and for a given length ofseparation of the electrodes, will carry a high and frequentlydestructive amount of current, I have discovered that, if conditions ofvery great purity are provided for in the separating electrodes and inthe atmosphere about them, no such stable arc will form. On thecontrary, an unstable, weak discharge, of transient and wanderingnature, appears and rapidly goes out, without apparent action upon theelectrodes.

For instance, when iron electrodes of very great purity are touched andthen separated, in an atmosphere of highly purified argon, the usualstable arc does not form, but rather a transient discharge of lowstability which rapidly goes out,

even with a separation of the electrodes and with an applied voltage of120 volts. Under ordinary conditions of purity, these voltage andarc-length conditions would give a stable arc and one destructive to theelectrodes. The iron in 4,5 this case was prepared by the repeatedsolution and extraction, by recrystallization, of iron oxalate from asolution of distilled water; the oxalate was heated to ferric oxide, theoxide reduced by hydrogen, as finely divided iron, and

was then sintered and swaged and drawn into a wire. The wire wasde-gasified by heating in a vacuum and sealed off in the evacuated glasstube while hot. After cooling in the evacuated glass tube, the iron maybe exposed to air at room 5 temperature without contamination. The argonwas purchased with a total purity content of approximately 99%, and wasfurther purified to a purity of about 99.3% to 99.6% by treatment forseveral hours in the discharge of a misch-metal arc formed in a bulbwhich was connected with 5 the arc-testing chamber. The impuritiescontained in the argon purchased were mostly nitrogen and water vaporand some carbonaceous gases. 'Misch metal is an alloy obtained in therare earth industry, containing cerium, lantha- 10 num, and other metalswhich absorb hydrogen strongly at room temperature, and react vigorouslywith oxygen and nitrogen at high temperatures. The high temperature formy purposes and for the vaporization of the metal is secured 15 byforming an arc of which the misch metal is one electrode. The metal thusvaporized reacts with all gases, except the inert ones, forming stablecompounds which condense on the walls of the chamber in which the mischarc is formed, and leave the inert gas highly purified. Under theseconditions of extreme purity, the above results were obtained.- But theywere not fully obtained if the process of purification was not thoroughand complete.-

Based on these facts, I have invented an appa ratus for and method ofinterrupting electrical -circuits, whether to function as a circuitbreaker or in commutation or in other applications Where non-arcingcircuit interruption is desired. This 30 process consists in withdrawinghighly purified metal conductors, preferably iron, as the terminals ofthe circuit, in an inert gas, preferably argon, of great purity, as theenvironment of the circuit interruption. 35

' I have found by experiment that I am able to produce satisfactoryarcless circuit interruption by the use of three of the five rare gases:helium, argon, neon, krypton, and xenon. It is indicated thatthe arclessinterruption thus obtained is made possible by a general property ofeach of the rare gases.

' The rare gases were of the purity which may be specified asspectroscopically free from active gases, although in at least oneinstance, it con- 45 sisted of a mixture of rare gases; for example,eight-tenths of a percent. of helium in neon. In other instances,freedom of the gases from active constituents was of the order of 99.3to 99.9 per cent. Under these conditions of lesser purity, the currentinterruption could be accomplished only I where smaller currents andlower voltages were involved. In this latter case currents of the orderof five to ten amperes were interrupted, whereas in the cases of morecomplete freedom from active constituents in the gases, currents of theorder of one hundred to one hundred fifty amperes were successfullyinterrupted without the forming of a stable arc.

I have observed that argonof 99.0 per cent. purity, the principalimpurity being nitrogen with a little water vapor and carbonaceousgases, is entirely unsuitable for the practice of my invention and givesa stable arc whenever a metallic circuit capable of forming an arc isbroken in this gas.

Concerning the metals used, three were tried, and all three of them wereused successfully. They were the metals zinc, silver and iron. The

zinc was of spectroscopic purity, having been produced by distillationin a vacuum. It was baked at 360 C. in order to drive outany residualgases which it might contain. The silver was 99.999 percent. pure butcontained spectroscopic traces of copper and iron. It likewise was bakedat 600 C. to drive out any gases which it might contain. Severaldiiferent grades of iron were used. While my earlier experimentsemployed iron as pure as could be obtained, an iron which was shown byanalysis to contain .07 per cent. oxygen and .0012 percent. hydrogen, mymore recent experiments indicate that ordinary commercial mild steelfunctions successfully, provided the gas is drastically purified, as,for example, by the action of the welding arc. Thus, in argon of 99.3 to99.6 percent. purity, ordinary steel electrodes are found to support astable are, carrying approximately one hundred fifty amperes for severalminutes. During this time, iron vapor is being liberated from theelectrode tips. This very hot iron vapor seems to serve as an excellentgetter or scavenger of any active gas molecules present, and combineswith such molecules to form oxides, nitrides, etc. These compounds arepushed away from the hot region of the are by the freshly liberatedvapors emanating from it. Once out in the cooler regions of the arc, thecompounds condense leaving the inert gas purified by their removal. Soonthe arc, operating now in a progressively purer atmosphere, becomesunstable and goes out of its own accord.

Under these conditions currents as high as 150 amperes can beinterrupted without the formation of a stable arc.

I therefore conclude that the provision of an inert gas sufficientlyfree from active contaminations is adequate for the operation of myinvention without the necessity of high purity in the electrodematerial.

I am consequently led to the following viewpoint:-

If the metals are spectroscopically pure and if the rare gases arespectroscopically free from active gases, the invention operates over awide range of currents, voltages and pressures. It operates for silver,zinc, and iron in argon and for iron also in neon and helium. Probablyit operates for all pure metals in all inert gases or mixtures of inertgases.

The purity of the electrodes may be spectroscopical in degree, but goodresults have been obtained in argon with the use of electrodes ofcommercial mild steel. In this case, it may be necessary to give adrastic purification to the gas just before the electrodes areseparated, but if the gas is pure, the invention operates even withimpure electrodes.

It is clear that the conditions of purity above described may beobtained in other than the above methods. -I do not wish, therefore, tobe limited to the above methods of purification, nor to the above metal(iron), nor gas (argon), but wish to patent a method and apparatus usingmetals or alloys preferably purified, but which may be only ofcommercial purity in an atmosphere of highly g purified inert gas forthe interruption of electrical circuits, under whatever conditions itmay be desirable to interrupt such circuits.

In the apparatus, which is diagrammatically represented in Fig. 1, pureiron electrodes A and 11 B are contained in a gas-tight electricallynonconducting container C, which, in this instance, is formed of glass;The electrode A is mounted fixedly in the container and the electrode B,

which is mounted in a guide, such as a tube, is 1| maintained in contactwith electrode A, by a coil spring D. Leads E and F of the circuit to beinterrupted are respectively connected with electrodes A and B. Theelectrode chamber is filled with pure argon gas, which is preferably ata 21 pressure of from 150 to 1200 mm. mercury, and especially above 760mm. mercury. I have used current at from zero to volts and from 1 toamperes, but have expected and intended that my invention would apply tocommercial currents 2.

and voltages. A solenoid, or electro-magnet G, placed either inside oroutside the container, is

provided for the purpose of overcoming the pressure of the spring D andretracting the movable electrode B from the stationary electrode A, and31 thus breaking the circuit.

If desired, a second container H, equipped with electrodes I and J toform a misch-metal arc may be attached at its top and bottom to thecontainer 0 respectively by tubes h and h in a.

order to maintain the purity'of the argon gas. All parts inside of thecontainer must be, as nearly as possible, gas free.

In Fig. 2, the pure iron electrodes K and L are mounted in a containerM, the upper portion v of which may be of metal or glass, and the lowerportion of which consists of a flexible metal bellows N which servesboth as the lower portion of the container and as mechanical meanstocause separation lof said terminals K and L.

Where the entire container is made of metal. the electrodes, or one ofthem, must of course be insulated from each other.

This application for patent is a continuation in part of my applicationfor Method of and 51 apparatus for substantially non-arcing circuitinterruption, Serial Number 589,638, filed January 29, 1932.

I claim:

1. A substantially non-arcing circuit breaker 5.

comprising a pair of iron electrodes, means for maintaining saidelectrodes in an atmosphere of argon of at least approximately 99.3%purity, and means for causing relative movement of said electrodes tobring them into and out of contact.

3. A substantially non-arcing circuit breaker 6:

comprising a pair of solid metal electrodes,.means for maintaining saidelectrodes in an atmos--- phere consisting of at-least 99.3% rare gasand means for causing relative movement of said m electrodes to bringthem into and out of contact 4. A structure as specified in claim 3, inwhich.

-the atmosphere consists of at least 99.3% rare gas consistingessentially of argon.

5. A structure as specified in claim 3 in which 7 9,158,074 '3 theatmosphere of at least 99.8% rare in an atmosphere of rare andsubjecting gas consisting essentially of neon. such gas to the action ofa misch-metal are 6. A structure as specified in claim 3 in which untilit is brought to a purity of at least 99.3%. the atmosphere consists ofat least 99.3% rare 8. A method as specifled in claim 'I in which gasconsisting essentially of helium. the electrodes are iron and theraregas employed 6 7. A method of preparing a substantially nonisargonof an initial purity of about 99% arcing circuit breaker which comprisesenclosing a pair of relatively movable solid electrodes G'I. E. DOAN.

